This invention relates to plastic film excellent in anti-static property and adhesive property as well as excellent in transparency, a process for preparing the same and a light-sensitive photographic material using said film.
A polyester film, particularly polyethylene terephthalate biaxially oriented film has been used as a base for photographic film, a base for drawing and a base for magnetic recording tape due to its transparency, dimensional stability and excellent mechanical properties. In these uses, a subbing layer has been usually provided between a polyester support and a surface material whereby adhesiveness between the support and the material has been improved.
On the other hand, for improvement in adhesiveness between a linear polyester and a metal foil, various plastics, particularly a hydrophilic resin such as gelatin, there has heretofore been proposed to use a water-soluble or water-dispersible polyester copolymer as a subbing layer on the merits of working atmosphere such as less toxicity and non-inflammability, and unnecessariness of explosion-proof facilities.
As an example thereof, for example, in Japanese Patent Publication No. 40873/1972, there has been described a copolymer using 8 mole % or more of an ester forming sulfonic acid metal base-containing compound based on a total acid component and 20 mole % or more of polyethylene glycol based on a total glycol component for the purpose of dispersing the polymer in water. However, when the copolymer is used as a subbing layer, it can be easily expected that water resistance of said subbing layer, i.e. water resistance of adhesion is lowered.
Also, in Japanese Patent Publication No. 5476/1981, a saturated linear aliphatic dicarboxylic acid having 4 to 8 methylene groups has been used for the purpose of improving adhesiveness. In this case, however, it cannot be said that water resistance of a subbing layer is sufficient. Further, in Japanese Provisional Patent Publication No. 88454/1981, a substantially water-insoluble aqueous dispersion has been used in order to improve water resistance, but a water-soluble organic solvent is contained in a dispersion so that there remains in the problem of working atmosphere. In Japanese Provisional Patent Publication No. 248231/1985, substantially the same material as in the aforesaid Japanese Provisional Patent Publication No. 88454/1981 has been disclosed, but the material is different therefrom mainly in the point of containing no organic solvent in the final aqueous dispersion. However, an organic solvent has been used in the course of preparing the aqueous dispersion so that it is not practically preferred in the points that, in addition to the problem of working atmosphere, preparation processes of the aqueous dispersion become complicated.
Also, in such a prior art, it is difficult to provide excellent transparency and antistatic property to a subbing layer simultaneously. In Japanese Provisional Patent Publication No. 164831/1986, a technique of providing a subbing layer which is transparent, has transparency and satisfies adhesiveness has been disclosed. However, a polyester copolymer to be used therein is substantially water-insoluble and yet the polyester copolymer is prepared as an aqueous dispersion after once dissolved in a water-soluble organic solvent, and then used for a subbing layer coating solution. Thus, the resulting subbing layer is inferior in adhesiveness to a hydrophilic colloid layer whereas it is excellent in water resistance. Further, for using the polyester copolymer as an aqueous dispersion, a water-soluble organic solvent is necessarily contained therein so that a problem of working atmosphere remains, and other various problems are involved that measures to explosion proof of an elongation device and environmental pollution should have been taken.